This invention relates to an improvement of the leveling valve disclosed in assignee's U.S. Pat. No. 5,161,579 entitled LEVELING VALVE FOR AIR SPRINGS. More specifically, this invention relates to a leveling valve for controlling the amount of air within an air spring mounted between two members, at least one of which is movable relative to the other. The leveling valve of this invention controls the air pressure in the air spring in response to changes in the distance between two such members and has its greater use in maintaining the constant level of a vehicle chassis or frame relative to its axles in response to the loading and unloading of the vehicle.
In assignee's U.S. Pat. No. 5,161,579, there is disclosed a leveling valve for air springs which incorporates in one body the actuating mechanism, a dampener, a valve means actuated by the actuating mechanism, an over-travel mechanism, and a pilot-operated dump means for dumping the air from the air spring through the valve. This feature is accomplished by providing an elongated body having an air inlet port, an air outlet delivery port, an air outlet exhaust port, and a valve means all located at one of the ends of the body. An actuator mechanism is located at the other end of the body and an elongated actuator extends essentially the entire length of the elongated body to the valve means.
One feature of U.S. Pat. No. 5,161,579 is an over-travel actuating mechanism which includes a valve travel limit and an over-travel means which provides for take up of the over-travel of the valve actuating mechanism. This is accomplished by a sliding sleeve located about a plunger and between two coil springs. The sleeve is actuated by two rotatable eccentric means mounted on the elongated valve body, one on each side of the sleeve. A forked actuator arm has a first arm connected to a rotatable eccentric means located on one side of the sleeve and a second arm connected to a rotatable eccentric means located on the other side of the sleeve. These two arms are actuated in response to changes in distance between two members between which an air spring is mounted.
Another feature of U.S. Pat. No. 5,161,579 is a means for quickly dumping the air from the air springs through an exhaust port. This is accomplished by providing a dump piston located in a separate piston cylinder that is in communication with a dump pilot port. The dump piston is actuated by subjecting it to air pressure introduced through the dump pilot port causing it to engage a snap ring on the plunger to open the valve means and provide communication between the delivery port and the exhaust port so that the air in the air bag is dumped or exhausted through the exhaust port.
Another unique feature of U.S. Pat. No. 5,161,579 is the construction of a dampener which is a separate self-contained member formed of a piston cylinder part and a cap connected to each other and having a piston mounted in the chamber between the parts. Extending from both sides of the piston are hubs exposed to the exterior of the dampener cylinder. The piston is interconnected to the plunger by a stop means extending radially from the plunger and located between the dampener and the valve means. The plunger is interconnected to the piston by a coil spring circumventing the plunger and extending between one of the hubs of the piston and the plunger actuating mechanism. Thus, the valve has the unique feature of two springs normally maintaining the plunger in the neutral position in which position the valve means is closed. The "time to travel" motion of the plunger for actuating the valve means is controlled by a viscous fluid moving from one side of the piston to the other.
Although the invention of U.S. Pat. No. 5,161,579 is a vast improvement over other leveling valves for air springs, in the further development of such leveling valve, as employees of the assignee of such patent, we have discovered improvements of such leveling valves. Specifically, one of such improvements is the construction of the sleeve as described above. In the sleeve of U.S. Pat. No. 5,161,579, the sleeve is one piece actuated by eccentrically-actuated dogs each having a cylindrical pin portion and a rectangular cam portion. The cam portion is extended into slots in the sleeve in which they are adapted to slide. In sliding within the slots, the wall of the slots and the dogs wear, creating accuracies in the actuation of the valve.
In accordance with the present invention, the sleeve is constructed of three parts including two end parts and a center part. Pins mounted eccentrically on rotatable members are connected to opposite sides of the center part and slideably actuate the center part along and transversely of the longitudinal axis of the plunger. Although wear may occur between the center part and the two end parts, the springs circumferentially mounted around the plunger force the end parts against the center part, taking up any wear that may occur on either or both of the center and end parts. Thus, the construction of our sleeve compensates for any wear in the sleeve. Further, the three-part sleeve maximizes the longitudinal forces exerted by the eccentric actuating means on the plunger while minimizing any forces transverse to the plunger.
Another unique feature of the present invention is the construction of the elongated actuator extending from the end of the elongated body where the eccentric actuating mechanism is located to the other end of the body where the valve means is located. In accordance with this invention, this elongated actuator means comprises the heretofore described plunger to a dampening piston, a dump piston, and another plunger. The dampening piston, dump piston, and said other plunger are formed as an integral one piece. In a more specific aspect of this feature of the invention, the first plunger is adjustably connected to the dampening piston whereby the length of the elongated actuator means within the elongated body can be adjusted. This is accomplished by providing a threaded hole extending into the dampening piston into which the threaded end of the first plunger is adjustable.
Another feature of this invention is the provision for a one-piece, molded dampening cylinder, dump cylinder, and guide for the second plunger referred to above. Such cylinders respectively receive the dampening piston, the dump piston, and the second plunger, all of which are molded into one piece.
Still another feature of our invention resides in a new and novel valve means which reduces air consumption, increases the life of the air compressor for supplying air to the air springs, and thus saves fuel and permits smaller compressors. Such valve construction also reduces the variation in the suspension ride height by metering and smoothing out the quantity of air flowing through the inlet exhaust ports. The metered flow of air through the exhaust port is accomplished by providing a pintel at the extreme end of the second plunger of the valve actuator, which end opens and closes communication between the inlet port and delivery port and the delivery port and exhaust port. The pintel is precisely dimensioned to create a metered air flow at the desired valve actuator lever angles. In other words, the diameter of the pintel controls the quantity of air flow through the exhaust port as the air springs adjust to find the proper height. The metering of the flow of air through the inlet port is accomplished by providing meter openings adjacent to and located upstream of the valve seat which is opened and closed by the second plunger.
Having described the novel and unique features of our invention, reference is now made to the drawings and the following description made in conjunction with the drawings.